The present invention encompasses fabric softener compositions adapted for use in the rinse cycle of a laundering operation. More specifically, the softener compositions herein comprise very small particles of a substantially water-insoluble, cationic fabric softening agent distributed in a liquid carrier. The small size of the particles, which accounts for their improved softening activity, is achieved by means of certain additives as described hereinafter.
Liquid fabric softening compositions have long been known in the art and are widely utilized by housewives during the wash and rinse cycles of automatic laundry operations. The term "fabric softening" as used herein and as known in the art refers to a process whereby a desirably soft handle and fluffy appearance are imparted to fabrics.
Compositions containing quaternary ammonium salts having at least one long chain hydrocarbyl group are commonly used to provide fabric softening benefits when used in laundry rinse operations. (See, for example, U.S. Pat. Nos. 3,364,142; 3,349,033; 3,546,115; 3,644,203; 3,733,463; also "Fabric Softeners and Their Evaluation", Manufacturing Chemist & Aerosol News, September, 1970, pages 39-45.) Although the various prior art softening compositions employing quaternary ammonium salts are effective for their intended purpose, there have been continuing efforts to provide more economical and effective fabric softening compositions.
Most liquid fabric softener compositions currently in use contain from about 3% to about 6% by weight of the softening agent dispersed in a carrier liquid. It might be assumed that to increase the effectiveness of such compositions it would merely be necessary to increase the level of softening agent. However, the use of high levels of softening agents is not economically attractive. More importantly, the use of excessively high concentrations of long-chain quaternary softeners in such compositions can result in an undesirable, greasy feel and a waterproofing effect on fabrics treated therewith. Accordingly, simply increasing the level of softening agent in such compositions is not an optimal means for increasing their effectiveness.
It has now been found that many prior art softening compositions, employed in the usual way by addition during the deep rinse cycle in an automatic washing machine, are not uniformly distributed over the fabric surfaces. Thus, certain areas of the fabric may receive relatively high levels of fabric softening agent, whereas other areas may receive little or none. This problem becomes particularly acute when the fabrics are folded or tangled, such that all surfaces are not exposed to the rinse liquor at the time the softener is added. Moreover, many housewives are wont to pour the fabric softener through the fabrics, where it is quickly absorbed, and do not make any particular effort to insure uniform distribution throughout the rinse bath.
It has now been found that by providing the fabric softening agent in a finely divided state, more uniform distribution throughout the rinse bath and on the fabrics can be secured. Accordingly, a substantial increase in softening effectiveness and uniformity can be secured without the need for increasing the concentration of softening agent in the composition. It has been found that dispersions of fabric softeners in the desired finely divided state can be provided by means of certain surfactants used in combination with long chain alcohols.
Moreover, it has now been found that the common cationic fabric softeners can lose much of their effectiveness in a rinse bath by virtue of the carryover of anionic surfactants from the wash cycle. When anionic surfactants are used to wash fabrics, they can be retained in substantial quantities on the fabric surfaces even after the spray rinse. Thus, when the softener is added to the final deep rinse, anionic surfactants may be present up to concentrations of 10 ppm, and greater, depending on machine design, surfactant usage, etc. These anionic surfactants undesirably interact with cationic fabric softeners, thereby detracting from their effectiveness. This problem is particularly acute inasmuch as a small proportion of anionic surfactant can flocculate a particle comprising many molecules of quaternary compound. Of course, the problem of interference by anionic surfactants can be overcome by very thoroughly rinsing the fabrics, or by completely avoiding anionic surfactants. However, since the average user is not disposed to take such extreme measures, it has been found to be advantageous to provide a material which will scavenge the undesirable anionic surfactants from the rinse bath, thereby preventing their interaction with the fabric softener. As will be seen hereinafter, certain water-soluble ethoxylated quaternary ammonium compounds are admirably suited for this purpose.
It is an object of the present invention to provide improved fabric softening compositions without recourse to excessive levels of softening agents.
It is another object of the present invention to provide compositions which achieve improved distribution of softener active throughout the aqueous rinse bath in an automatic washing machine.
Another object herein is to provide fabric softener compositions containing various additives which enhance the softening activity of the cationic fabric softeners.
These and other objects are obtained herein as will be seen by the following disclosure.